VEGF ameliorates pulmonary hypertension through inhibition of endothelial apoptosis in experimental lung fibrosis in rats
Laszlo Farkas, … , Mark Inman, Martin Kolb
Laszlo Farkas, … , Mark Inman, Martin Kolb
Published April 20, 2009
Citation Information: J Clin Invest. 2009;119(5):1298-1311. https://doi.org/10.1172/JCI36136.
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Research Article Pulmonology

VEGF ameliorates pulmonary hypertension through inhibition of endothelial apoptosis in experimental lung fibrosis in rats

Abstract

Idiopathic pulmonary fibrosis (IPF) can lead to the development of secondary pulmonary hypertension (PH) and ultimately death. Despite this known association, the precise mechanism of disease remains unknown. Using a rat model of IPF, we explored the role of the proangiogenic and antiapoptotic growth factor VEGF in the vascular remodeling that underlies PH. In this model, adenoviral delivery of active TGF-β1 induces pulmonary arterial remodeling, loss of the microvasculature in fibrotic areas, and increased pulmonary arterial pressure (PAP). Immunohistochemistry and mRNA analysis revealed decreased levels of VEGF and its receptor, which were inversely correlated with PAP and endothelial cell apoptosis in both the micro- and macrovasculature. Treatment of IPF rats with adenoviral delivery of VEGF resulted in reduced endothelial apoptosis, increased vascularization, and improved PAP due to reduced remodeling but worsened PF. These data show that experimental pulmonary fibrosis (PF) leads to loss of the microvasculature through increased apoptosis and to remodeling of the pulmonary arteries, with both processes resulting in PH. As administration of VEGF ameliorated the PH in this model but concomitantly aggravated the fibrogenic process, VEGF-based therapies should be used with caution.

Authors

Laszlo Farkas, Daniela Farkas, Kjetil Ask, Antje Möller, Jack Gauldie, Peter Margetts, Mark Inman, Martin Kolb

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Figure 7

Increased vascular density, decreased EC apoptosis, decelerated vascular remodeling, and improved PH in AdTGF-β1/AdVEGF animals.

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Increased vascular density, decreased EC apoptosis, decelerated vascular...
(A and C) Representative images of CD34 IHC for AdTGF-β1/AdVEGF (A) and AdTGF-β1/AdDL70 (B) at day 7. (C) Representative CD34 and α-SMA double immunofluorescence of AdTGF-β1/AdVEGF animal at day 14: no vascularization within α-SMA+ fibroblastic foci (dotted lines) but augmented capillary density in adjacent areas (arrows). Original magnification, ×400. Scale bars: 50 μm. (D–J) Increased CD31+ (D) and CD34+ (E) area in highly fibrotic regions (Ashcroft 6–8) of AdTGF-β1/AdVEGF animals. AdTGF-β1/AdVEGF animals have reduced EC apoptosis in highly fibrotic regions (Ashcroft 6–8) at day 7 as shown by quantitative double immunofluorescence for caspase-3+CD31+ (F), caspase-3+CD34+ (G), TUNEL+CD31+ (H), and TUNEL+CD34+ (I). Augmented VEGFR2 phosphorylation of ECs (P-VEGFR2+CD34+ cells) is found for Ashcroft 6–8 areas (day 7) of AdTGF-β1/AdVEGF animals in J. (K–O) mPAP is decreased in AdTGF-β1/AdVEGF (K). The development of vascular remodeling is decelerated in AdTGF-β1/AdVEGF. MWT for small (ED < 50 μm, L) and medium (50 μm ≤ ED < 100 μm, M) PA. Apoptosis of PA EC in small (N) vessels is lower in severely fibrotic areas (Ashcroft 6–8) of AdTGF-β1/AdVEGF at day 7. For medium PA, a trend is found (O). Data confirmed by cleaved caspase-3 (not shown). Black bars show AdTGF-β1/AdDL70; white bars show AdTGF-β1/AdVEGF. Each bar represents mean ± SEM of 5–6 animals per group (D, E, and K–M) or 3–4 animals per group (F–J, N, and O). *P < 0.05; **P < 0.01; ***P < 0.0001, 1-way ANOVA or Student’s t test.